Comparative study between photodynamic and antibiotic therapies for treatment of footpad dermatitis (bumblefoot) in Magellanic penguins (Spheniscus magellanicus)

Strengthening collaborations at the Biology-Physics interface: trends in antimicrobial photodynamic therapy

The unbridled use of antimicrobial drugs over the last decades contributed to the global dissemination of drug-resistant pathogens and increasing rates of life-threatening infections for which limited therapeutic options are available. Currently, the search for safe, fast, and effective therapeutic strategies to combat infectious diseases is a worldwide demand. Antimicrobial photodynamic therapy (APDT) rises as a promising therapeutic approach against a wide range of pathogenic microorganisms. APDT combines light, a photosensitizing drug (PS), and oxygen to kill microorganisms by oxidative stress. Since the APDT field involves branches of biology and physics, the strengthening of interdisciplinary collaborations under the aegis of biophysics is welcome. Given this scenario, Brazil is one of the global leaders in the production of APDT science. In this review, we provide detailed reports of APDT studies published by the Laboratory of Optical Therapy (IPEN-CNEN), Group of Biomedical Nanotechnology (UFPE), and collaborators over the last 10 years. We present an integrated perspective of APDT from basic research to clinical practice and highlight its promising use, encouraging its adoption as an effective and safe technology to tackle important pathogens. We cover the use of methylene blue (MB) or Zn(II) porphyrins as PSs to kill bacteria, fungi, parasites, and pathogenic algae in laboratory assays. We describe the impact of MB-APDT in Dentistry and Veterinary Medicine to treat different infectious diseases. We also point out future directions combining APDT and nanotechnology. We hope this review motivates further APDT studies providing intuitive, vivid, and insightful information for the readers.

In vitro porphyrin-based photodynamic therapy against mono and polyculture of multidrug-resistant bacteria isolated from integumentary infections in animals

Multidrug-resistant (MDR) organisms have been frequently isolated from integumentary lesions of animals, and these lesions are usually infected by more than one pathogen. This study evaluated an in vitro antimicrobial photodynamic therapy (aPDT) using two water-soluble tetra-cationic porphyrins (3-H₂TMeP and 4-H₂TMeP) against mono and polyculture of MDR bacteria isolated from dogs, cats, and horses. Ten isolates of MDR bacteria (two of each species: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens, and Staphylococcus pseudointermedius) were used to evaluate aPDT against the monoculture using a non-cytotoxic concentration of 3-H₂TMeP and 4-H₂TMeP porphyrins (40 µM), with 30 min of light irradiation in Gram-positive and 90 min for Gram-negative bacteria. The aPDT using the 4-H₂TMeP porphyrin was also tested against five different polycultures (Coagulase positive Staphylococcus (CPS) and Pseudomonas sp.; E. coli and Proteus sp.; Pseudomonas sp. and Proteus sp.; CPS and E. coli; and CPS and Proteus sp.) for 90 min. The efficacy of both treatments was evaluated by plating the solution exposed to light or kept in the dark and counting the colonies forming units after 24 h of incubation at 37 °C. Atomic force microscope analysis was used to map bacteria morphological changes and extract adhesion force parameters from the bacteria membranes. Only the 4-H₂TMeP porphyrin had antibacterial activity against MDR bacteria in monoculture, especially S. pseudointermedius and P. aeruginosa. In polyculture, the 4-H₂TMeP porphyrin reduced bacterial concentrations (p < 0.05) in the associations of E. coli and S. pseudointermedius, P. aeruginosa and S. pseudointermedius, and P. aeruginosa and P. mirabilis. These results showed that aPDT using 4-H₂TMeP is a good option for future associations of aPDT and other therapies or in vivo research.

Injectable Anesthesia With Medetomidine, Ketamine, and Butorphanol in Captive Humboldt Penguins (Spheniscus humboldti)

The effects of an injectable anesthesia with 0.05 mg/kg medetomidine, 5 mg/kg ketamine, and 0.5 mg/kg butorphanol administered together intramuscularly were evaluated in 22 captive Humboldt penguins (Spheniscus humboldti, 10 male and 12 female), with a mean age of 8.5 ± 8.23 years. The birds fasted for18-24 hours prior to the procedure. Induction was followed by 4 distinct progressive responses of the birds to the anesthetic effect, including onset of initial effects at 2.0 ± 1.7 minutes (x̄ ± SD), sternal recumbency with the head still elevated at 2.2 ± 1.6 minutes, lowering and placing the beak tip to the ground at 3.6 ± 3.4 minutes, and lateral positioning of the neck and head at 4.2 ± 3.4 minutes. A general state of sedation, muscle relaxation, and analgesia were noted 10.0 ± 2.8 minutes postinjection. However, according to an established scoring system for the assessment of anesthetic depth in avian patients, a surgical plane of anesthesia was not achieved. Muscle relaxation determined by the same scoring system lasted for 31.4 ± 17.1 minutes. The penguins' mean respiratory rate did not demonstrate significant change and spontaneous ventilation was present throughout the procedure. Relative peripheral arterial oxygen saturation decreased significantly from 92.83 ± 5.77% at 10 minutes to 90.91 ± 5.77% at 40 minutes following induction. The birds' heart rate also decreased significantly from 112.55 ± 23.97 beats/min at 10 minutes to 101.65 ± 25.42 beats/min at 40 minutes. The measured cloacal temperatures were maintained within normal range despite ambient temperatures of up to 28.3°C (82.9°F). Reversal of medetomidine with 0.25 mg/kg atipamezole was conducted after 45.1 ± 7.3 minutes. Recovery was smooth but of variable duration with patients being able or willing to stand steadily in an upright position after 50.1 ± 34.6 minutes. One penguin died during recovery from a ruptured left ventricle and consecutive pericardial tamponade, but no predisposing factors were identified. The anesthetic protocol proved to be effective for noninvasive and minor painful procedures (eg, diagnostic imaging, blood collection). Disadvantages to the administration of the combined anesthetic agents in the penguins included a short period of muscle relaxation and smooth but potentially prolonged recovery. The safety of the anesthetic protocol described for Humboldt penguins in this report has to be evaluated critically against the the death of 1 penguin during recovery.

Methylene blue-mediated antimicrobial photodynamic therapy can be a novel non-antibiotic platform for bovine digital dermatitis

BACKGROUND

Bovine digital dermatitis (BDD) is one of the most important diseases that effect dairy cows. Methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) emerges as a promising technique to treat superficial infections in bovines.

METHODS

Twenty BDD lesions located at the skin horn transition of the claw of pelvic limbs of 16 cows were treated by MB-APDT, using a red LED cluster (λ = 660 nm, irradiance =60 mW/cm², exposure time = 40 s) combined with topical application of MB at 0.01 %; or by topical application of OXY (500 mg in 20 % solution). Each lesion was treated twice with an interval of 14 days. Lesions were weekly evaluated until day 28 by clinical analysis and by histological examination on days 0 and 28.

RESULTS

Both treatments led to a similar reduction of lesions area. At day 28, three lesions treated by OXY did not present completely recovery, whereas no lesions were observed in MB-APDT group. OXY resulted in a slight increase in type I and III collagen levels, while MB-APDT led to a significant increase in the total area of both collagen types. An abundant number of spirochetes were histologically observed in all lesions before treatments. On the 28th day, five lesions treated by OXY still presented a slight number of spirochetes, whereas in MB-APDT group no spirochetes were evidenced.

CONCLUSION

Our findings suggest that MB-APDT is more effective than OXY and could be used in Veterinary practice to fight BDD.

Antimicrobial photodynamic therapy can be an effective adjuvant for surgical wound healing in cattle

BACKGROUND

Rumenostomy is a useful procedure commonly performed in cattle for medical treatment of domestic ruminants with forestomach diseases. Methylene blue (MB)-mediated antimicrobial photodynamic therapy (APDT) has been broadly investigated to treat infected wounds.

AIM

The aim of the study was to evaluate the effectiveness of MB-mediated APDT (MB-APDT) combined with chlorhexidine and zinc oxide ointment on wound healing process after rumenostomy.

METHODS

Fourteen Nelore bulls were subjected to rumenostomy procedure. Animals were randomly divided into MB-APDT (MB associated with a red diode laser performed immediately after surgery and repeated on days 3, 5, 7 and 10) and control groups. Daily care included topical cleaning with chlorhexidine 2% followed by topical zinc oxide ointment. Animals were followed-up until the 28th day.

RESULTS

Wounds presented a better post-surgical profile in MB-APDT group when it was compared with the control group. In MB-APDT group, it was also possible to observe less pain on palpation of wounds borders, less edema and inflammatory exudate. Additionally, animals from MB-APDT group were faster discharged from the cattle care facility.

CONCLUSION

Our results support the use of MB-APDT for the post-surgical management of rumenostomy. This pilot study ratifies the use of APDT in cattle and also suggests that it could be performed for other surgical procedures as a complementary approach or an alternative for topical administration of antibiotics.

Pododermatitis in raptors admitted in a wildlife rehabilitation centre in central spain

Pododermatitis is a chronic and progressive bacterial infectious disease of birds´ footpads, especially associated with captivity, which could represent an important problem in wildlife rehabilitation centres, delaying the release of the birds to the environment and harming their conservation. The objectives of the present study were i) to estimate the incidence rate of pododermatitis, ii) to analyse the influence of environmental, physiological, and pathological factors which may influence the onset of the infection in raptors after their admission to a rehabilitation centre, and iii) to follow up the evolution and macroscopic characteristics of the lesion. An observational retrospective study was carried out on clinical cases of raptors (n = 2004) admitted in a rehabilitation centre in central Spain from 2009 to 2015. The proportion of pododermatitis was 6.9%, with an incidence density of 6.8 cases/100 bird-years at risk. Our results showed that the disease was more likely to occur in birds staying longer (P < 0.001). According to Cox analysis, the variables 'raptor family' (P < 0.001) and 'age' (P = 0.002) may have significant effects on pododermatitis development. Raptors from the Falconidae and Strigidae families were less likely to develop pododermatitis than those from the Accipitridae family, with a hazard ratio (HR) of 0.31 and 0.13, respectively. Regarding age, fully feathered raptors had a three-fold higher risk of having pododermatitis than non-fully feathered birds. Survival analysis of time of pododermatitis development revealed significant differences associated with the variables 'raptor family' (P < 0.03); 'age' (P < 0.001) and 'cause of admission' (P = 0.001). Duration of the pathology (P < 0.05) and lesion location (P < 0.001) seemed to be phylogenetic dependent. Injuries were primarily located in the toes area or the whole footpad of birds belonging to the Accipitridae or Falconidae families, respectively (P = 0.003).

Technological Advances in Wound Treatment of Exotic Pets

Although most research about the use of technological advances for wound healing was performed in laboratory animals but oriented to human medicine, recent technological advances allowed its application not only to small animals but also to exotic pets. This article reviews the literature available about some of these techniques (negative wound pressure therapy, photobiomodulation [laser therapy], electrical stimulation therapy, therapeutic ultrasonography, hyperbaric oxygen therapy), and other advances in wound management (skin expanders, xenografts, and bioengineered autologous skin substitutes) in exotic pet species.

Draft genome sequence of an extensively drug-resistant Pseudomonas aeruginosa isolate belonging to ST644 isolated from a footpad infection in a Magellanic penguin (Spheniscus magellanicus)

OBJECTIVES

The incidence of multidrug-resistant bacteria in wildlife animals has been investigated to improve our knowledge of the spread of clinically relevant antimicrobial resistance genes. The aim of this study was to report the first draft genome sequence of an extensively drug-resistant (XDR) Pseudomonas aeruginosa ST644 isolate recovered from a Magellanic penguin with a footpad infection (bumblefoot) undergoing rehabilitation process.

METHODS

The genome was sequenced on an Illumina NextSeq^® platform using 150-bp paired-end reads. De novo genome assembly was performed using Velvet v.1.2.10, and the whole genome sequence was evaluated using bioinformatics approaches from the Center of Genomic Epidemiology, whereas an in-house method (mapping of raw whole genome sequence reads) was used to identify chromosomal point mutations.

RESULTS

The genome size was calculated at 6436450bp, with 6357 protein-coding sequences and the presence of genes conferring resistance to aminoglycosides, β-lactams, phenicols, sulphonamides, tetracyclines, quinolones and fosfomycin; in addition, mutations in the genes gyrA (Thr83Ile), parC (Ser87Leu), phoQ (Arg61His) and pmrB (Tyr345His), conferring resistance to quinolones and polymyxins, respectively, were confirmed.

CONCLUSION

This draft genome sequence can provide useful information for comparative genomic analysis regarding the dissemination of clinically significant antibiotic resistance genes and XDR bacterial species at the human-animal interface.

Antimicrobial photodynamic therapy for infectious stomatitis in snakes: Clinical views and microbiological findings

BACKGROUND

Antimicrobial photodynamic therapy (APDT) has been broadly investigated as an alternative to treat localized infections, without leading to the selection of resistant microorganisms. Infectious stomatitis is a multifactorial disease frequently reported in captive snakes characterized by infection of the oral mucosa and surrounding tissues. In this study, we investigated methylene blue (MB)-mediated APDT to treat infectious stomatitis in snakes and verified the resistance phenotype and genotype before and after APDT.

METHODS

Three Boid snakes presented petechiae, edema and caseous material in their oral cavities. MB (0.01%) was applied on the lesions and after 5min they were irradiated using a red laser (λ=660nm), fluence of 280J/cm², 8J and 80s per point, 100mW, spot size 0.028cm² and fluence rate of 3.5W/cm². APDT was repeated once a week during 3 months. Samples of the lesions were collected to identify bacteria and antibiotic resistance profiles. To analyze the clonality of bacterial isolates before and after APDT, isolates were subjected to ERIC PCR analysis.

RESULTS

Snakes presented clinical improvement such as reduction of inflammatory signs and caseous material. Pseudomonas aeruginosa and Escherichia coli were present in all snakes; Klebsiella pneumoniae and Morganella morganii were also identified in some animals. We also observed that the oral microbiota was completely replaced following APDT. However, K. pneumoniae isolates before and after APDT were a single clone with 100% of genetic similarity that lost resistance phenotype for seven antibiotics of four classes.

CONCLUSIONS

These results show that APDT can be used to treat infectious stomatitis in snakes.

In vivo probiotic and antimicrobial photodynamic therapy as alternative therapies against cryptococcosis are ineffective

Cryptococcosis, an invasive fungal infection distributed worldwide that affects both domestic and wild animals, has incredible rates regarding treatment failure, leading to the necessity of the development of new therapies. In this way, we aimed to evaluate the probiotic (Saccharomyces boulardii, Lactobacillus paracasei ST-11, and Lactobacillus rhamnosus GG) and antimicrobial photodynamic alternative therapies against Cryptococcus gattii in a murine model. Although previous studies suggest that these therapies can be promising against cryptococcosis, our experimental conditions for both probiotic and antimicrobial photodynamic therapies (aPDT) were not able to improve the survival of mice with cryptococcosis, even with the treatment combined with fluconazole. Our results may help other researchers to find the best protocol to test alternative therapies against Cryptococcus gattii.

Advances in antimicrobial photodynamic inactivation at the nanoscale

The alarming worldwide increase in antibiotic resistance amongst microbial pathogens necessitates a search for new antimicrobial techniques, which will not be affected by, or indeed cause resistance themselves. Light-mediated photoinactivation is one such technique that takes advantage of the whole spectrum of light to destroy a broad spectrum of pathogens. Many of these photoinactivation techniques rely on the participation of a diverse range of nanoparticles and nanostructures that have dimensions very similar to the wavelength of light. Photodynamic inactivation relies on the photochemical production of singlet oxygen from photosensitizing dyes (type II pathway) that can benefit remarkably from formulation in nanoparticle-based drug delivery vehicles. Fullerenes are a closed-cage carbon allotrope nanoparticle with a high absorption coefficient and triplet yield. Their photochemistry is highly dependent on microenvironment, and can be type II in organic solvents and type I (hydroxyl radicals) in a biological milieu. Titanium dioxide nanoparticles act as a large band-gap semiconductor that can carry out photo-induced electron transfer under ultraviolet A light and can also produce reactive oxygen species that kill microbial cells. We discuss some recent studies in which quite remarkable potentiation of microbial killing (up to six logs) can be obtained by the addition of simple inorganic salts such as the non-toxic sodium/potassium iodide, bromide, nitrite, and even the toxic sodium azide. Interesting mechanistic insights were obtained to explain this increased killing.

INTRAVENOUS REGIONAL ANTIBIOTIC PERFUSION THERAPY AS AN ADJUNCTIVE TREATMENT FOR DIGITAL LESIONS IN SEABIRDS

Foot infections are a common problem among seabirds in wildlife rehabilitation. Pododermatitis and digital infections are often challenging to treat because of the presence of suboptimal substrates, abnormal weight-bearing due to injuries, and suboptimal nutritional or health status. Seabirds represent the majority of animals requiring rehabilitation after oil spills, and foot problems are a common reason for euthanasia among these birds. Antibiotic intravenous regional perfusion therapy is frequently used in humans and other species to treat infections of the distal extremities, but it has not been evaluated in seabirds. During the 2015 Refugio oil spill response, four birds with foot lesions (pododermatitis, osteomyelitis, or both) were treated with ampicillin/sulbactam administered intravenously to the affected limb(s) in addition to systemic antibiotics and anti-inflammatories. Three of the birds, all brown pelicans ( Pelecanus occidentalis ) recovered rapidly and were released. Two of these birds had acute pododermatitis and were treated once with intravenous regional perfusion. They were released approximately 3 wk after the perfusion therapy. The third pelican had osteomyelitis of a digit. It was treated twice with intravenous regional perfusion and was released about 1 mo after the initial perfusion therapy. The fourth bird, a Pacific loon ( Gavia pacifica ), was treated once with perfusion therapy but did not respond to treatment and was euthanatized. No serious adverse effects were observed. This technique should be explored further in avian species.

The photodynamic efficiency of phenothiazinium dyes is aggregation dependent

Effectiveness increased in the order of Azure A < Azure B < Methylene Blue while aggregation increased in the order of Methylene Blue < Azure B < Azure A.